The Influence of Different Strategies for the Saccharification of the Banana Plant Pseudostem and the Detoxification of Concentrated Broth on Bioethanol Production.

Abstract

Pseudostem of the Musa cavendishii banana plant was submitted to chemical pretreatments with acid (H2SO4 2%, 120°C, 15 min) and with alkali (NaOH 3%, 120°C, 15 min), saccharified by commercial enzymes Novozymes® (Cellic CTec2 and HTec2). The influences of the pretreatments on the degradation of the lignin, cellulose and hemicellulose, porosity of the surface, particle crystallinity, and yield in reducing sugars after saccharification (Y RS), were established. Different concentrations of biomass (70 and 100g/L in dry matter (dm)), with different physical differences (dry granulated, crushed wet bagasse, and whole pseudostem), were used. The broth with the highest Y RS among the different strategies tested was evaporated until the concentration of reducing sugars (RS) was to the order of 100g/L and fermented, with and without prior detoxification with active carbon. Fermentation was carried out in Erlenmeyer flasks, at 30°C, initial pH 5.0, and 120rpm. In comparison to the biomass without chemical pretreatment and to the biomass pretreated with NaOH, the acid pretreatment of 70g/L of dry granulated biomass enabled greater digestion of hemicellulose, lower index of cellulose crystallinity, and higher Y RS (45.8±0.7%). The RS increase in fermentation broth to 100g/L, with posterior detoxification, presented higher productivity ethanol (Q P=1.44±0.02 g/L/h) with ethanol yield (Y P/RS) of 0.41±0.02g/g. The value of Q P was to the order of 75% higher than Q P obtained with the same broth without prior detoxification.